(Calibre
= The normal diameter of the bore of a gun barrel measured across the
lands)

The history of shell
design practically begins with the introduction of rifled guns in the
middle of the nineteenth century as the result of the recommendations
of a Royal Commission in 1858. The cannon ball presents no design problems.
Spherical shell, said to have been first made at Greenwich in 1543,
were little used except for shore bombardments up to the Napoleonic
Wars. Between 1815 and 1850, however, the 8-inch shell gun firing a
66 lb shell and alsosolid
shot and shrapnel, invented in 1797, was mounted in many ships. In the
Crimean War the attack on Sebastopol in 1854 made it clear that wooden
ships could not stand up to these shell, while the attack on Kinburn
in 1855 showed that armour was a complete answer to them. Cylindrical
shell with pointed heads had already been demonstrated in rifled guns
in 1850, and following the commissions recommendations shell rotated
by studs were adopted.

The first shell
introduced were nose or base-fuzed common shell, made of iron and filled
with powder. They were about 3 calibres in length and 1.5-2 calibre
radius ogival heads. Palliser shell and shot (invented by Sir William
Palliser in 1863, for the attack of armour), shrapnel shell, double
shell about 4 calibres long, for attack of wooden ships at short range
and case shot were also supplied. The Palliser shell were 2 to 2.5 calibres
in length, made of iron, the head being chilled in casting to harden
it. They were powder-filled but had no fuze, the shock of impact being
relied on to set off the filling. Palliser shot were similar, but had
a smaller cavity and no filling. These types were supplied for guns
of 7 inch calibre and over. Shrapnel shell differed little from those
in use up to 1918.

In the 1880s the
breech-loader replaced the muzzle-loader and studs were dropped, being
replaced at first by the Elswick gas check and then by the present type
of driving band which had been developed by Krupp and had already been
in use abroad for some years.

Armour-piercing
shell in steel replaced the iron Palliser shell in the 1880s. From that
time until 1911, when Lyddite was adopted, the cavity was usually left
unfilled, as powder exploded too soon on the heavier armour then in
use. Penetrative caps were introduced in Russia and America in 1894,
but were not adopted in the British Navy until 1903.

Lyddite was adopted
for common shell in 1895 and iron was replaced by steel, which had not
been used previously as powder would not fragment it properly. The standard
length of 3.1 calibres laid down in 1860 was still adhered to at the
end of the century, but the head shape of 1.58 c.r.h. laid down at the
same time had altered to 2 c.r.h. In 1908, after a series of trials,
an 8 c.r. head was recommended on ballistic grounds, but as it was found
that with the limits of length imposed by stowage arrangements in existing
ships the capacity of common pointed shell would be too small, 4 c.r.h.
was fixed as a compromise. This led to the adoption of Firths
hollow cap, from which developed the separate ballistic cap. Base plates
were introduced for Lyddite shell in 1909, and in 1912 tracers were
approved.

The latter were
proposed in 1903 by Semple but the first trials were not satisfactory.
Between 1901 and 1910 there was considerable discussion regarding the
best anti T.B.D. weapon. After a number of trials it was rec.mmended
that common nose-fuzed shell should be used in preference to common
pointed, shrapnel or the special light shell which had been proposed.

The First World
Warand in particular experience at the Battle of Jutland brought
some changes in shell types. Piercing shell were adopted for 4.7-inch
and smaller guns and the designs of large piercing shell, which were
considered to have proved unsatisfactory in action, were further studied.
Up to 1918 all shell of this type were proved against plates at normal.
It was realised that this did not represent actual battle conditions,
and in 1918 tests against plate at 20 degrees, increased in 1929 to
30 degrees, were added. Star shell, which had been developed in 1893
but not adopted, were also ordered, following their use by the Germans
at Jutland. At first multi-star designs were tried, but these were superseded
almost at once by single star types with parachutes. T.N.T. largely
replaced Lyddite T.N.T./B.W.X., Amatol and Shellite were tried, the
latter being adopted as the standard filling for armour-piercing shell
in 1919.

Between 1919 and
1933 there was little change in shell design, research being mainly
concentrated on improving the large piercing shell and on the development
of smoke shell. Between 1933 and 1939 new shell with nose fuzes of increased
weight and improved ballistics for the medium and for the new dual-purpose
guns were developed. The Second World War saw the introduction of new
fillingsincluding R.D.X. and aluminised typesbase-ejection
smoke, target and radar shell, and the
'K device for piercing and practice shell.

FACTORS
INFLUENCING DESIGN

The factors
which govern the design of shell may be grouped under the following
headings:

the effect
which it is required to produce at the target

requirements
arising from the conditions in the gun on firing

requirements
for satisfactory flight, which may be sub-divided into considerations
for drag, stability and accuracy.

Effect
at target

This is the basis
of classification of shell. There are four main groups

Piercing
shell.

In these the main
consideration is that the shell should penetrate armour and should,
after passing through, be capable of exploding effectively. As much
explosive as possible (consistent with the strength necessary for penetrating
the type of armour that a shell of the given calibre can be expected
to defeat) is carried in the armour piercing and the semi armour piercing
shell. In the new class of H.E.P. shell an increase in capacity to a
good figure for fragmentation and blast is the basis of design and a
reduced penetration is accepted, the shell being designed for attack
of lightly armoured ships or superstructures.

H.E.
(High Effect) Shell.

In these penetration
is not a requirement, most of them being burst on impact or by a time
or proximity fuze, although some are intended to pass through light
plating or the skin of an aeroplane. Where the design is not restricted
by other factors, fragmentation is the main consideration. More attention
is now being paid to blast effect.

Special shell.

Shell with fillings
for special effects which have been designed include marker, chemical
and incendiary shell. The first produces a distinctive burst to mark
the fall of shot. The others introduce chemical or incendiary agents
into a ship, either by bursting inside it or by a follow-through action
following a burst on the plating. Chemical shell might also be required
for shore bombardment.

Shell not intended for effect against a target.

These include base-ejection
shell (with : a few designs of forward-ejection) such as star, B.E.
smoke, radar echo and target shell. They also include practice proof
and drill shell and shot.

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